[Stackmap] Materialize the jump address within the patchpoint noop slide.

This patch moves the jump address materialization inside the noop slide. This
enables patching of the materialization itself or its complete removal. This
patch also adds the ability to define scratch registers that can be used safely
by the code called from the patchpoint intrinsic. At least one scratch register
is required, because that one is used for the materialization of the jump
address. This patch depends on D2009.

Differential Revision: http://llvm-reviews.chandlerc.com/D2074

Reviewed by Andy

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194306 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 22 insertions, 3 deletions

diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
index fa15114..2cc038c 100644
--- a/lib/Target/X86/X86MCInstLower.cpp
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -785,6 +785,7 @@ static void LowerPATCHPOINT(MCStreamer &OutStreamer,
                 !MI.getOperand(0).isImplicit();
   unsigned StartIdx = hasDef ? 1 : 0;
 #ifndef NDEBUG
+  {
   unsigned StartIdx2 = 0, e = MI.getNumOperands();
   while (StartIdx2 < e && MI.getOperand(StartIdx2).isReg() &&
          MI.getOperand(StartIdx2).isDef() &&
@@ -793,8 +794,20 @@ static void LowerPATCHPOINT(MCStreamer &OutStreamer,
 
   assert(StartIdx == StartIdx2 &&
          "Unexpected additonal definition in Patchpoint intrinsic.");
+  }
 #endif
 
+  // Find the first scratch register (implicit def and early clobber)
+  unsigned ScratchIdx = StartIdx, e = MI.getNumOperands();
+  while (ScratchIdx < e &&
+         !(MI.getOperand(ScratchIdx).isReg() &&
+           MI.getOperand(ScratchIdx).isDef() &&
+           MI.getOperand(ScratchIdx).isImplicit() &&
+           MI.getOperand(ScratchIdx).isEarlyClobber()))
+    ++ScratchIdx;
+
+  assert(ScratchIdx != e && "No scratch register available");
+
   int64_t ID = MI.getOperand(StartIdx).getImm();
   assert((int32_t)ID == ID && "Stack maps hold 32-bit IDs");
 
@@ -812,10 +825,16 @@ static void LowerPATCHPOINT(MCStreamer &OutStreamer,
                     getStackMapEndMOP(MI.operands_begin(), MI.operands_end()),
                     isAnyRegCC && hasDef);
 
-  // Emit call. We need to know how many bytes we encoded here.
-  unsigned EncodedBytes = 2;
+  // Emit MOV to materialize the target address and the CALL to target.
+  // This is encoded with 12-13 bytes, depending on which register is used.
+  // We conservatively assume that it is 12 bytes and emit in worst case one
+  // extra NOP byte.
+  unsigned EncodedBytes = 12;
+  OutStreamer.EmitInstruction(MCInstBuilder(X86::MOV64ri)
+                              .addReg(MI.getOperand(ScratchIdx).getReg())
+                              .addImm(MI.getOperand(StartIdx + 2).getImm()));
   OutStreamer.EmitInstruction(MCInstBuilder(X86::CALL64r)
-                              .addReg(MI.getOperand(StartIdx + 2).getReg()));
+                              .addReg(MI.getOperand(ScratchIdx).getReg()));
 
   // Emit padding.
   unsigned NumNOPBytes = MI.getOperand(StartIdx + 1).getImm();